The remarkable progress of the semiconductor technology has brought about numerous technological revolutions in the field of home appliances. High-performance home appliances which involve systems which were too large to be commercialized by the prior art discrete circuit configurations have recently been successfully supplied to the market due to the reduced cost of the microcomputers, LSI, large-capacity memories and the like.
High-performance products with a high added value, however, generally include an operating section with a number of operating keys complicating the handling procedures, resulting in an increased risk of erroneous operation of the system due to users' operating errors. This is especially true because heating apparatuses are mainly used by ordinary housewives who, unlike audio set enthusiasts, are not interested in multi-function equipment which is complicated to operate. Further, misuse of a heating apparatus often causes a heating failure of the food to be cooked and in an extreme case may lead to an accident such as a fire in and outside of the heating chamber.
In addition, a system comprised of electronic circuits is liable to be operated erroneously by spurious noise signals. Factors causing malfunctions of an electronic device are varied and include spike noises from the power line, radiation noise coming directly into the system, and static electricity. The most adverse malfunction of the heating apparatus which is caused by such physical factors are those concerning control of the heating means. It actually sometimes happens that an undesired heating process is started or heating still continues after the lapse of a predetermined heating time. These malfunctions, like the above-mentioned malfunctions due to personal factors, are particularly dangerous because they may result in loss of human life or property by causing a fire.
Therefore, the most important requirement in system safety design for heating apparatus including electronic circuits is to prevent the two great personal and physical errors of misuse and malfunctions, and to quickly inform the user of any case of such misuse or malfunctions.
The object of the present invention is to provide a safety device using a voice synthesizer for the heating apparatus for preventing the two errors of misuse and malfunctions and informing the user quickly of any case of such troubles.